Terrorism poses a threat to the travelling public. Threat devices, such as weapons, or threat materials, such as explosives, may be carried in pockets or strapped to the body with little probability of detection by casual, or even skilled, observers. Therefore, it has become common practice to require the travelers to divest themselves of outer garments, belts, wallets, jewelry, mobile phones, and shoes when entering or passing through a critical facility such as an airport, train depot, or public building. The divesting procedure is time consuming and inconvenient for members of the public and is expensive to manage for the facility operator.
Once divested, the garments and accessories are typically scanned using an X-ray transmission imaging system while the member of the public is scanned by a different piece of technology, such as a millimeter wave imaging system or X-ray backscatter imaging system, to produce images of the body of the person being scanned. The images of the body may contain anomalies caused by items carried by the person. These anomalies may be innocuous items, such as a passport or a handkerchief, or may be significant threats, such as an explosive material. Currently, known technologies require a trained algorithm to analyze the shape of the detected object to determine if it is a threat or if it is innocuous. From the shape alone, however, it is difficult to assess the nature of many potential threats, or indeed innocuous items, and therefore false alarm rates tend to be significant.
Therefore, what is needed is a system for material specific detection using non-ionizing radiation in which focused beams of low intensity microwave radiation are projected in rapid succession at an individual as they walk through a portal.